Adjustment mechanism for motorized multi-way seat adjustment

ABSTRACT

An adjustment mechanism for a seat comprises at least one screw shaft ( 111, 112 ) and a motor for driving the at least one screw shaft ( 111, 112 ). Further, the adjustment mechanism comprises at least one nut element ( 121, 122 ) engaged with the at least one screw shaft ( 121, 122 ) in such a way that a rotation of the at least one screw shaft ( 111, 112 ) caused by the motor translates into a linear motion of the at least one nut element ( 121, 122 ). In a first range of the linear motion of the at least one nut element ( 121, 122 ) the linear motion translates into adjustment of the seat according to a first degree of freedom, and in a second range of the linear motion of the at least one nut element ( 121, 122 ) the linear motion translates into adjustment of the seat according to a second degree of freedom.

FIELD OF THE INVENTION

The present invention relates to an adjustment mechanism for a seat andto a seat equipped with such adjustment mechanism. The invention relatesin particular to an adjustment mechanism for motorized multi-wayadjustment of a seat.

BACKGROUND OF THE INVENTION

In view of optimizing comfort of a seat, it is known to provide the seatwith various kinds of adjustability. By way of example, it is known toadjust a vehicle seat with respect to inclination of a backrest portionof the seat, with respect to height of a headrest of the seat, or withrespect to arching and/or vertical position of a lumbar support of theseat.

To facilitate adjustment of the seat, it is also known to implementadjustment of the seat in a motorized manner. For example, WO2017/032390 A1 describes a motorized adjustment mechanism which can beused for adjusting various seat components. EP 2 698 278 A1 describes amotorized adjustment mechanism for a headrest which may be used forshifting the headrest in a forward/backward direction or for adjustingthe position of side bolsters of the headrest.

However, in such known adjustment mechanisms, a separate adjustmentmechanism and motor is may need to be provided for each adjustmentdegree of freedom. For example, EP 2 698 278 A1 describes usage of twoseparate actuators in the headrest of the seat, one being provided foradjustment of the headrest in a forward/backward direction, the otherbeing provided for height adjustment of the headrest.

Accordingly, there is a need for adjustment mechanisms which allow forefficiently adjusting a seat according to multiple degrees of freedom.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an adjustment mechanism according toclaim 1 and a seat according to claim 14. The dependent claims definefurther embodiments.

Accordingly, an adjustment mechanism according to an embodiment has thepurpose of being used in a seat, for adjusting the seat according to atleast two degrees of freedom. Examples of such degrees of freedom aretilting of one or more flap elements, such as side bolsters or a legsupport, horizontal movement of a headrest of the seat in aforward/backward direction, vertical movement of the headrest of theseat, length adjustment of a seat cushion portion of the seat, heightadjustment of a lumbar support of the seat, or adjustment of arching ofa lumbar support of the seat.

According to an embodiment, the adjustment mechanism comprises at leastone screw shaft and a motor for driving the at least one screw shaft.Further, the adjustment mechanism comprises at least one nut elementengaged with the at least one screw shaft in such a way that a rotationof the at least one screw shaft caused by the motor translates into alinear motion of the at least one nut element. In a first range of thelinear motion of the at least one nut element the linear motiontranslates into adjustment of the seat according to a first degree offreedom, and in a second range of the linear motion of the at least onenut element the linear motion translates into adjustment of the seataccording to a second degree of freedom. Accordingly, the same motor andthe same screw shaft may be used for implementing adjustment accordingto different degrees of freedom. The adjustment mechanism may thus beimplemented in a compact and efficient manner.

According to an embodiment, the first degree of freedom corresponds todisplacement of a headrest of the seat in a horizontal direction or totilting of the headrest. The headrest may then comprise at least oneflap element, e.g., side bolsters, which is pivotable with respect to amain portion of the headrest, and the second degree of freedom maycorrespond to pivoting of the at least one flap element with respect tothe main portion of the headrest. Accordingly, horizontal displacementor tilting of the headrest may be efficiently combined with tilting ofthe flap element(s).

According to an embodiment, the headrest comprises a first flap elementwhich is pivotable with respect to the main portion of the headrest andsecond flap element which is pivotable with respect to the main portionof the headrest. The first and second flap elements may for examplecorrespond to right and left side bolsters of the headrest. The seconddegree of freedom may then correspond to pivoting of the first flapelement and the second flap element with respect to the main portion ofthe headrest. In this case the adjustment mechanism may comprise a firstnut element engaged with the at least one screw shaft and a second nutelement engaged with the at least one screw shaft. The first nut elementand the second nut element may be engaged with a first threaded portionand a second threaded portion of the same screw shaft, with one of thefirst threaded portion and the second threaded portion being righthanded and the other being left handed. Rotation of the screw shaft inone direction would thus cause the linear movements of the first andsecond nut elements to be in opposite directions. Alternatively, thefirst nut element and the second nut element may be engaged withdifferent screw shafts. In this case, the direction of the linearmovements of the first and second nut elements may also be determined bythe respective rotation direction of the screw shafts and/or which eachmay either have a right handed thread or a left handed thread.

In the above case of using the first nut element and the second nutelement, a rotation of the at least one screw shaft caused by the motortranslates into a linear motion of the first nut element and a linearmotion of the second nut element. In a first range of the linear motionof the first nut element and a first range of the linear motion of thesecond nut element, the linear motion of the first nut element and ofthe second nut element may translate into adjustment of the seataccording to the first degree of freedom. Further, in a second range ofthe linear motion of the first nut element the linear motion of thefirst nut element may translate into pivoting of the first flap elementwith respect to the main portion of the headrest, while in a secondrange of the linear motion of the second nut element the linear motionof the second nut element translates into pivoting of the second flapelement with respect to the main portion of the headrest. Accordingly,the two flap elements may be tilted in an efficient manner by using thelinear motion of the two nut elements in the second range.

The tilting of the at least one flap element may be about a verticaltilt axis. In this case, the adjustment mechanism may be efficientlyimplemented by arranging the at least one screw shaft in a horizontaldirection.

According to an embodiment, the adjustment mechanism comprises at leastone further screw shaft and a clutch mechanism for selectively engagingthe motor with one or more of the at least one screw shaft and the atleast one further screw shaft. In this case, a rotation of the at leastone further screw shaft caused by the motor may translate intoadjustment of the seat according to a third degree of freedom. Forexample, the adjustment mechanism may comprise at least one further nutelement engaged with the at least one further screw shaft such thatrotation of the at least one further screw shaft translates into alinear motion of the at least one further nut element. The linear motionof the at least one further nut element may then translate intoadjustment of the seat according to the third degree of freedom. Thethird degree of freedom may for example correspond to displacement of aheadrest of the seat in a vertical direction, i.e., to a heightadjustment of the headrest. In this case, it may be beneficial if the atleast one screw shaft is arranged in a horizontal direction and the atleast one further screw shaft is arranged in a vertical direction.

Accordingly, additional degrees of freedom may be efficiently supportedby providing the clutch mechanism.

According to an embodiment, the clutch mechanism comprises at least onesolenoid actuator for switching the clutch mechanism between a firststate in which the motor is engaged with one or more of the screw shaftsand second state in which the motor is not engaged with said one or moreof the screw shafts. The solenoid actuator may be controlledelectronically.

According to an embodiment, the clutch mechanism comprises at least oneshape memory alloy (SMA) actuator for switching the clutch mechanismbetween a first state in which the motor is engaged with one or more ofthe screw shafts and second state in which the motor is not engaged withsaid one or more of the screw shafts. The SMA actuator may be controlledelectronically.

According to an embodiment, the adjustment mechanism is configured to beaccommodated within the headrest. Accordingly, the adjustable seat maybe implemented in a compact manner, by efficiently using space which isavailable within the headrest.

According to a further embodiment, a seat is provided, e.g., a vehicleseat. The seat comprises an adjustment mechanism as defined above. Usingthis adjustment mechanism, the seat can be adjusted according to two ormore degrees of freedom. As mentioned above, examples of such degrees offreedom are tilting of one or more flap elements, such as side bolstersor a leg support, horizontal movement of a headrest of the seat in aforward/backward direction, vertical movement of the headrest of theseat, length adjustment of a seat cushion portion of the seat, heightadjustment of a lumbar support of the seat, or adjustment of arching ofa lumbar support of the seat.

Accordingly, in some embodiments the seat comprises a headrest. In thiscase the adjustment mechanism may be used for adjustments according todegrees of freedom related to the headrest and may be accommodatedwithin the headrest. In this way, a compact design of the seat may beachieved. Further, distances over which force and/or torque needs to betransmitted may be limited, which may help to improve efficiency,durability, and reliability.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention will be described with reference to theaccompanying drawings.

FIGS. 1A and 1B illustrate an adjustable seat according to an embodimentof the invention.

FIGS. 2A, 2B, and 2C illustrate an adjustment mechanism for adjustmentof the headrest of the seat according to multiple degrees of freedom.

FIGS. 3A, 3B, and 3C illustrate adjustment of the headrest by horizontaldisplacement of the headrest.

FIGS. 4A, 4B, and 4C illustrate adjustment of the headrest by tiltingflap elements of the headrest.

FIGS. 5A and 5B illustrate adjustment of the headrest by verticaldisplacement of the headrest.

FIG. 6 illustrates a clutch mechanism of the adjustment mechanism.

FIGS. 7A and 7B illustrate different states of the clutch mechanism.

FIG. 8 illustrates a further clutch mechanism which may be used in anadjustment mechanism according to an embodiment of the invention.

FIG. 9 illustrates a still further clutch mechanism which may be used inan adjustment mechanism according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Exemplary embodiments of the invention will be described with referenceto the drawings. While some embodiments will be described in the contextof specific fields of application, such as in the context of a vehicleseat, the embodiments are not limited to this field of application. Thefeatures of the various embodiments may be combined with each otherunless specifically stated otherwise.

FIGS. 1A and 1B schematically illustrate an adjustable seat 10.Specifically, FIGS. 1A and 1B illustrated various degrees of freedom ofadjusting the seat 10. In the illustrated example, it is assumed thatthe seat 10 is a vehicle seat, in particular a driver's seat or apassenger seat for a car. However, it is noted that similarconfigurations could also be used for other types of seats, e.g., seatsfor other types of vehicles, such as trucks, aircrafts or trains, orseating furniture.

As illustrated, the seat 10 comprises a seat cushion portion 20, abackrest portion 30, and a headrest 50. The backrest portion 30 may beprovided with a lumbar support 40, e.g., configured as a wire basket oras a flexible plastic element. The seat 10 is assumed to be adjustableaccording to various degrees of freedom, illustrated by double-headedarrows. As illustrated, these degrees of freedom may include:displacement of the headrest 50 in a horizontal direction, denoted byHH, displacement of the headrest 50 in a vertical direction, denoted byHV, displacement of the lumbar support 40 in a horizontal direction,denoted by LH, adjustment of arching of the lumbar support 40, denotedby LA, adjustment of a horizontal length of the seat cushion portion 20,denoted by SL, and tilting of a leg support at a front edge of the seatcushion portion 20, denoted by LF. Here, a “horizontal” direction refersto a normal installation position of the seat and substantiallycorresponds to a direction within a plane of the seat cushion portion20. In particular, a horizontal displacement as described herein maycorrespond to a displacement along a forward/backward direction, theforward direction corresponding to a direction from a back edge BE ofthe seat cushion portion 20, where the backrest portion 30 is attached,to an opposing front edge FE of the seat cushion portion 20, and thebackward direction corresponding to a direction from the front edge FEto the back edge BE. A “vertical” direction refers to a direction alongthe backrest portion 30. The vertical direction is typicallysubstantially perpendicular to the horizontal direction. The verticaldirection may also be referred to as upward/downward direction, with theupward direction corresponding to a direction from the seat cushionportion 20 towards the headrest 50 and the downward directioncorresponding to a direction from the headrest 50 towards the seatcushion portion 20. It is noted that in some situations, e.g., when thebackrest portion 30 is tilted backwards into a sleeping position, thevertical or upward/downward direction may also deviate from a directionwhich is perpendicular to the horizontal direction.

As illustrated in FIG. 1A, the adjustability of the length of the seatcushion portion 20 may be implemented by providing the seat cushionportion 20 with a seat cushion element 25 which is slidable in theforward/backward direction with respect to a main part of the seatcushion portion 20. The above-mentioned tiltable leg support may beprovided by a flap element 26 on a front edge side of the slidable seatcushion element 25.

FIG. 1B shows a schematic top view of the headrest 50. As furtherillustrated in FIG. 1B, a further degree of freedom for adjustment ofthe seat 10 may correspond to adjustment of side bolsters of theheadrest 50, denoted by BA. In particular, the headrest 50 may beprovided with a main portion 51, a first flap element 52 on a right sideof the main portion 51, and a second flap element 53 on a left side ofthe main portion 51. As illustrated, the flap elements 52, 53 can betilted about a vertical axis with respect to the main portion 51 of theheadrest 51. The flap element 52 thus defines an adjustable right sidebolster of the headrest, and the flap element 53 defines an adjustableleft side bolster of the headrest 50.

It is noted that the above degrees of freedom for adjustment of the seat10 are to be understood as a non-exhaustive list of examples ofadjustability. Accordingly, adjustment according to all of these degreesof freedom does not need to be supported by the seat 10, or the seat 10could also support adjustment according to one or more other degrees offreedom.

In the examples as further explained in the following, it is assumedthat adjustment of the seat 10 according to at least two degrees offreedom is implemented in a motorized manner, using a single motor. Anexample of a corresponding adjustment mechanism will now be furtherexplained with reference to FIGS. 2A, 2B, 2C, 3A, 3B, 3C, 4A, 4B, 4C,5A, 5B, 6, 7A, and 7B. In this example, it is assumed that theadjustment mechanism provides motorized adjustment of the seat 10 byhorizontal displacement of the headrest 50, i.e., according to thedegree of freedom denoted by HH, by vertical displacement of theheadrest 50, i.e., according to the degree of freedom denoted by HV, andtilting of the side bolsters of the headrest 50, i.e., according to thedegree of freedom denoted by BA. However, it is to be noted that asimilar configuration of the adjustment mechanism could also be used foradjustment according to other combinations of two or more degrees offreedom.

FIGS. 2A, 2B, and 2C show top views of the headrest 50 in differentadjustment states, with the adjustment mechanism being exposed forpurposes of illustration. Specifically, FIG. 2A illustrates the headrest50 in a neutral position, FIG. 2B illustrates the headrest 50 with themain portion of the headrest 50 being displaced out of the neutralposition in the forward direction, and FIG. 2C illustrates the headrest50 with the flap elements 52, 53 being tilted out of the neutralposition. The adjustment mechanism couples the main portion 51 and theflap elements 52, 53 to a bracket 55, by means of which the headrest 50is attached to the backrest portion 30 of the seat 10. The adjustmentmechanism is based on a spindle drive and uses screw shafts 111, 112 (orspindles) for driving the motorized adjustment. As illustrated, thescrew shafts 111, 112 extend horizontally in opposite directions from acentral part of the adjustment mechanism. A first nut element 121 isengaged with the first screw shaft 111, and a second nut element 122 isengaged with the second screw shaft 112. The first nut element 121 andthe second nut element 122 are movable along the respective screw shaft111, 112, but locked with respect to a rotation about the screw shaft111, 112. Accordingly, a rotation of the screw shaft 111, 112 translatesinto a linear movement of the respective nut element 121, 122 along thescrew shaft 111, 112. In the illustrated example, it is assumed that thefirst screw shaft 111 and the second screw shaft 112 are formed onopposite ends of a single drive shaft. Accordingly, rotation of thisdrive shaft produces a corresponding rotation of the first screw shaft111 and the second screw shaft 112, which in turn translates into thelinear movement of the nut elements 121, 122. One of the first screwshaft 111 and the second screw shaft 112 is assumed to have aleft-handed thread, while the other of the first screw shaft 111 and thesecond screw shaft 112 has a right handed thread. Accordingly, if thedrive shaft is rotated in a certain direction, the linear movements ofthe not elements 121, 122 will be in opposite directions.

As further illustrated, the main portion 51 of the headrest 50 iscoupled by levers 131, 132 to the bracket 55. The levers 131, 132 areeach supported to be rotatable about a vertical tilt axis. In a firstrange of the linear movement of the nut elements 121, 122, the nutelement 121 is engaged with the lever 131, and the nut element 122 isengaged with the lever 132. This has the effect that the linearmovements of the nut elements 121, 122 translate into rotation of thelevers 131, 132, which in turn displaces the main portion 51 of theheadrest 50 in the forward/backward direction, as illustrated in FIG.2B.

As further illustrated, the flap element 52 of the headrest 50 iscoupled by a lever 141 to the bracket 55, and the flap element 53 of theheadrest is coupled by a lever 142 to the bracket 55. The levers 141,142 are each supported to be rotatable about a vertical tilt axis. In asecond range of the linear movement of the nut elements 121, 122, thenut element 121 is engaged with the lever 141, and the nut element 142is engaged with the lever 142. This has the effect that the linearmovements of the nut elements 121, 122 translate into rotation of thelevers 141, 142, which in turn tilts the flap elements 52, 53 of theheadrest 50, as illustrated in FIG. 2C.

It is noted that while in FIGS. 2A, 2B, and 2C the displacement of themain portion 51 of the headrest 50 in the/backward direction isillustrated as occurring without moving the flap elements 52, 53, it isalso possible to couple movement of the flap elements 52, 53 in theforward/backward direction to the movement of the main portion 51 in theforward/backward direction. This may for example be achieved by couplingthe flap elements 52, 53 to the main portion 51, e.g., by upholsteryelements and/or a common cover, and/or by providing a support on themain portion 51, such as illustrated by short dotted lines in FIG. 2A.Accordingly, the adjustment mechanism may also be used for horizontaldisplacement of the headrest 50 as whole.

FIGS. 3A, 3B, and 3C further illustrate the adjustment of the headrest50 by horizontal displacement of the main portion 51 of the headrest 50.Specifically, FIGS. 3A, 3B, and 3C further illustrate actuation of thelever 131 by the nut element 121. Here, it is to be understood that thelever 132 will be actuated in a corresponding manner by the nut element122.

FIG. 3A illustrates a state in which the nut element 121 and the lever131 are in a neutral position and not yet engaged with each other. Byrotation of the screw shaft 111 in a first direction, the nut element121 may be moved towards the lever 131, until it eventually engages withthe lever 131, as illustrated in FIG. 3B. By further rotation of thescrew shaft 111 in the first direction, the nut element 121 is urgedagainst the lever 131, causing rotation of the lever 131 and forwarddisplacement of the main portion 51 of the headrest 50, until reaching amaximum displacement position as illustrated in FIG. 3C. When rotatingthe screw shaft 111 in the opposite direction, the lever 131 isgradually allowed to return to its neutral position. This returnmovement may for example be driven by spring force. For example, thelever 131 could be coupled to a spring element which is deformed whenrotating the lever 131 out of its neutral position, or the lever 131could itself exhibit a spring characteristic.

FIGS. 4A, 4B, and 4C illustrate adjustment of the headrest by tiltingthe flap elements 52, 53 of the headrest 50. Specifically, FIGS. 4A, 4B,and 4C further illustrate actuation of the lever 141 by the nut element121. Here, it is to be understood that the lever 142 will be actuated ina corresponding manner by the nut element 122.

FIG. 4A illustrates a state in which the nut element 121 and the lever141 are in a neutral position and not yet engaged with each other. Byrotation of the screw shaft 111 in a second direction which is oppositeto the above-mentioned first direction, the nut element 121 may be movedtowards the lever 141, until it eventually engages with the lever 141,as illustrated in FIG. 4B. By further rotation of the screw shaft 111 inthe second direction, the nut element 121 is urged against the lever141, causing rotation of the lever 141 and tilting of the flap element52 of the headrest 50, until reaching a maximum tilt position asillustrated in FIG. 4C. When rotating the screw shaft 111 in theopposite direction, the lever 141 is gradually allowed to return to itsneutral position. This return movement may for example be driven byspring force. For example, the lever 141 could be coupled to a springelement which is deformed when rotating the lever 141 out of its neutralposition, or the lever 141 could itself exhibit a spring characteristic.

Accordingly, FIGS. 3B and 3C define limits of the above-mentioned firstrange of the linear movement of the nut element 121, and FIGS. 4B and 4Cdefine limits of the above-mentioned second range of the linear movementof the nut element 121. Here, it is noted that in the illustratedexample the first range and the second range are separated, i.e., do notoverlap. However, it would also be possible to have some overlap of thefirst range and the second range. In this case, a part of thedisplacement of the main portion 51 would occur simultaneously with thetilting of the flap elements 52, 53.

FIGS. 5A and 5B illustrate further adjustment of the headrest 50 byvertical displacement. Specifically, FIGS. 5A and 5B show rear views ofthe headrest 50 in different vertical positions, with the adjustmentmechanism being exposed for purposes of illustration. FIG. 5Aillustrates the headrest 50 its lowermost position and FIG. 5Billustrates the headrest 50 being displaced upwardly from the lowermostposition.

As illustrated in FIGS. 5A and 5B, the adjustment mechanism includes athird screw shaft 113, which extends in vertical direction. A third nutelement 123 is engaged with the third screw shaft 113 and connected tothe bracket 55. The third screw shaft 113 and the third nut element 123provide a vertically adjustable coupling of the headrest 50 to thebracket 55. In particular, rotation of the third screw shaft 113 willcause a linear movement of the third nut element 123 of the third screwshaft 113, thereby vertically displacing the headrest 50, as illustratedby FIGS. 5A and 5B.

FIGS. 5A and 5B further illustrate the motor 150, which in theillustrated example is used for driving the first screw shaft 111, thesecond screw shaft 112, and the third screw shaft 113. The motor 150 maybe an electric motor and may be electronically controlled to adjust theseat 10. The motor 150 may for example be a brushless motor, e.g., usingan electronic commutation scheme. Implementing the motor 150 as abrushless motor may help to reduce noise and/or improve durability andreliability. Since motor 150 is used for driving both screw shafts 111,112 and usage of multiple motors is therefore not necessary, excessivecosts for using a brushless motor can be avoided.

For coupling the motor 150 to the screw shafts 111, 112, 113, theadjustment mechanism is provided with gears 155, 180 and a clutchmechanism 160 as further explained below. The gear 155 is a two-stageworm gear which facilitates a compact implementation of the adjustmentmechanism and at the same time allows for efficient adaptation of arevolution speed of the motor 150 to a desired rotation speed of thescrew shafts 111, 112, 113. The gear 180 is a worm gear used fortranslation of a rotation along the horizontal axis of the first andsecond screw shafts 111, 112 and the vertical axis of the third screwshaft 113. The clutch mechanism 160 allows for selectively engaging themotor 150 either with the first and second screw shafts 111, 112 or withthe third screw shaft 113. The clutch mechanism 160 is provided with anactuator 170 which allows for electronically controlling a state of theclutch mechanism 160. In particular, the actuator 170 may be used forelectronically switching the clutch mechanism 160 between a first state,in which the motor 150 is engaged with the first and second screw shafts111, 112 and a second state, in which the motor 150 is engaged with thethird screw shaft 113. In the illustrated example, the actuator 170 isassumed to be a solenoid actuator. However, other types of actuatorcould be used as well. As for example further explained below, also anSMA based actuator could be used for switching between the states of theclutch mechanism 160.

By using the clutch mechanism 160 to engage the motor 150 with the thirdscrew shaft 113 while disengaging the motor 150 from the first andsecond screw shafts 111, 112, the motor 150 can be used for exclusivelydriving the third screw shaft 113, thereby allowing to adjust thevertical position of the headrest 50, without vertically displacing theheadrest 50 or tilting the flap elements 52, 53 of the headrest 50.Similarly, by using the clutch mechanism 162 engage the motor 150 withthe first and second screw shafts 111, 112 while disengaging the motor150 from the third screw shaft 113, the motor 150 can be used forexclusively driving the first and second screw shafts 111, 112, therebyallowing to vertically displace the main portion 51 of the headrest 50and/or to tilt the flap elements 52, 53 of the headrest 50, whilemaintaining the vertical position of the headrest 50.

FIG. 6 further illustrates the clutch mechanism 160 of the adjustmentmechanism. As illustrated, the clutch mechanism 160 includes a firstgear wheel 161 which is driven by the two-stage worm gear 155. Asmentioned above, the first and second screw shaft 111, 112 are formed asdifferent portions of the same drive shaft. The first gear wheel 161 isarranged concentrically with this drive shaft, but is rotatable aboutthe drive shaft. Accordingly, a rotation of the first gear wheel 161does not necessarily translate into a rotation of the drive shaft. Nextto the first gear wheel 161, also concentrically with the axis of thedrive shaft, a first clutch wheel 163 is arranged on the drive shaft.The first clutch wheel 163 rotates together with the drive shaft. Thefirst gear wheel 161 and the first clutch wheel 163 have opposing axialfaces which are configured to be used for selectively engaging the firstgear wheel 161 and the first clutch wheel 163 by bringing the opposingaxial faces together. As further explained below, the first gear wheel161 and the first clutch wheel 163 may be provided with axiallyextending teeth on their respective axial face, and the first gear wheel161 and the first clutch wheel 163 may be engaged by interlocking ofthese axially extending teeth. For facilitating engagement and/ordisengagement of the axial teeth, the axial teeth may have sloped matingfaces, e.g., inclined by an angle of 5° or less with respect to theaxial direction. However, it is noted that other ways of engaging thefirst gear wheel 161 and the first clutch wheel 163 could be used aswell, e.g., engagement by surface friction. If the first clutch wheel163 is engaged with the first gear wheel 161, the drive shaft and thusalso the first and second screw shafts 111, 112 rotate together with thefirst gear wheel 161, i.e., are driven by the motor 150. If the firstclutch wheel 163 is disengaged from the first gear wheel 161, thedriveshaft and thus also the first and second screw shafts 111, 112 donot rotate together with the first gear wheel 161, i.e., are not drivenby the motor 150.

The clutch mechanism further includes a second gear wheel 164 arrangedon a further drive shaft 181 which is arranged in parallel to the driveshaft of the first and second screw shafts 111, 112. The second gearwheel 164 is engaged with the first gear wheel 161. Accordingly, themotor 150 drives the second gear wheel 164 through the first gear wheel161. The second gear wheel 164 is arranged concentrically with thefurther drive shaft 181 while being rotatable about the further driveshaft 181. Accordingly, a rotation of the second gear wheel 164 does notnecessarily translate into a rotation of the further drive shaft 181.Next to the second gear wheel 164, concentrically with the axis of thefurther drive shaft 181, a second clutch wheel 166 is arranged on thefurther drive shaft 181. The second clutch wheel 166 rotates togetherwith the further drive shaft 181. The second gear wheel 164 and thesecond clutch wheel 166 have opposing axial faces which are configuredto be used for selectively engaging the second gear wheel 164 and thesecond clutch wheel 166 by bringing the opposing axial faces together.As further explained below, also the second gear wheel 164 and thesecond clutch wheel 163 may be provided with axially extending teeth ontheir respective axial face, and the second gear wheel 164 and thesecond clutch wheel 166 may be engaged by interlocking of these axiallyextending teeth. For facilitating engagement and/or disengagement of theaxial teeth, the axial teeth may have sloped mating faces, e.g.,inclined by an angle of 5° or less with respect to the axial direction.However, it is noted that other ways of engaging the second gear wheel164 and the second clutch wheel 166 could be used as well, e.g.,engagement by surface friction. If the second clutch wheel 166 isengaged with the second gear wheel 164, the further drive shaft 181rotates together with the second gear wheel 164, i.e., is driven by themotor 150. Through the worm gear 180, the further drive shaft 181 thendrives the third screw shaft 113. If the second clutch wheel 166 isdisengaged from the second gear wheel 164, the further drive shaft 181and thus also the third screw shaft 113 does not rotate together withthe second gear wheel 166, i.e., is not driven by the motor 150.

The actuator 170 is used for controlling engagement of the first clutchwheel 163 with the first gear wheel 161 and engagement of the secondclutch wheel 166 with the second gear wheel 164. This is accomplished byaxial shifting of the first clutch wheel 163 on the drive shaft of thefirst and second screw shafts 111, 112, and by axial shifting of thesecond clutch wheel 166 on the further drive shaft 181. This is furtherillustrated in FIGS. 7A and 7B.

FIG. 7A illustrates the clutch mechanism 160 in the first state, inwhich the motor 150 is engaged with the first and second screw shafts111, 112 and disengaged from the third screw shaft 113. As can be seen,in the first state an effector end 171 of the actuator 170 is extendedby a travel distance D. The effector end 171 is coupled to both thefirst clutch wheel 163 and the second clutch wheel 166. As a result, thefirst clutch wheel 163 is shifted towards the first gear wheel 161, andthe second clutch wheel 166 is shifted away from the second gear wheel164. Accordingly, the first clutch wheel 163 engages with the first gearwheel 161, while the second clutch wheel 166 is disengaged from thesecond gear wheel 164. As illustrated, the engagement of the firstclutch wheel 163 with the first gear wheel 161 is achieved byinterlocking of axial teeth 162 of the first gear wheel 161 withcomplementary axial teeth of the first clutch wheel 163. Forfacilitating engagement and/or disengagement of the axial teeth 162 ofthe first gear wheel 161 with the complementary axial teeth of the firstclutch wheel 163, the axial teeth 162 and complementary axial teeth mayhave sloped mating faces, e.g., inclined by an angle of 5° or less withrespect to the axial direction. Due to the sloped mating faces, theaxial teeth 162 have an outer shape which tapers toward the first clutchwheel 163 and fits into a narrowing gap between two neighboringcomplementary teeth of the first clutch wheel 163. However, other waysof engaging the first clutch wheel 163 with the first gear wheel 161could be used as well.

FIG. 7B illustrates the clutch mechanism 160 in the second state, inwhich the motor 150 is engaged with the third screw shaft 113 anddisengaged from the first and second screw shafts 111, 112. As can beseen, in the second state the effector end 171 of the actuator 170 isretracted. As a result, the first clutch wheel 163 is shifted away fromthe first gear wheel 161, and the second clutch wheel 166 is shiftedtowards the second gear wheel 164. Accordingly, the first clutch wheel163 is disengaged from the first gear wheel 161, while the second clutchwheel 166 engages with the second gear wheel 164. As illustrated, theengagement of the second clutch wheel 166 with the second gear wheel 164is achieved by interlocking of axial teeth 165 of the second gear wheelwith complementary axial teeth of the second clutch wheel 166. Forfacilitating engagement and/or disengagement of the axial teeth 165 ofthe second gear wheel 165 with the complementary axial teeth of thesecond clutch wheel 166, the axial teeth 165 and complementary axialteeth may have sloped mating faces, e.g., inclined by an angle of 5° orless with respect to the axial direction. Due to the sloped matingfaces, the axial teeth 165 have an outer shape which tapers toward thesecond clutch wheel 166 and fits into a narrowing gap between twoneighboring complementary teeth of the second clutch wheel 166. However,other ways of engaging the second clutch wheel 166 with the second gearwheel 164 could be used as well.

As can be seen, the adjustment mechanism of the illustrated example maybe used for efficiently controlling adjustment of the seat 10 accordingto the different degrees of freedom by a single motor, namely forcontrolling horizontal displacement of the headrest 50, in particularfor controlling displacement of the main portion 51 of the headrest 50in the forward/backward direction, for adjusting the side bolsters ofthe headrest 50 by tilting the flap elements 52, 53, and for controllingdisplacement of the headrest 50 in the vertical direction, i.e., foradjusting the height position of the headrest 50. The adjustmentmechanism may be implemented in a compact manner which allows foraccommodating the adjustment mechanism within the headrest 50.

It is noted that while the above example referred to adjustment of theseat 10 according to the different degrees of freedom, a similaradjustment mechanism could also be used for controlling the seat 10according to only two degrees of freedom, e.g., only for controllingonly the horizontal displacement of the headrest 50 and the tilting ofthe flap elements 52, 53. Still further, as an alternative or inaddition to controlling the horizontal or vertical displacement of theheadrest 50, the adjustment mechanism could also be used for controllingtilting of the headrest 50. Furthermore, in addition or as analternative to the above examples of controlling degrees of freedomrelated to adjustment of the headrest 50, the adjustment mechanism couldalso be used for controlling degrees of freedom related to adjustment ofthe backrest portion 30, such as adjustment of the lumbar support 40 bycontrolling vertical displacement of the lumbar support 40 and/orarching of the lumbar support 40, and/or degrees of freedom related tothe seat cushion portion 20, such as controlling the length of the seatcushion portion 25 by controlling horizontal displacement of the seatcushion element 25 and/or adjustment of leg support by controllingtilting of the flap element 26. Depending on the controlled degrees offreedom, the adjustment mechanism could also be accommodated within thebackrest portion 30 or the seat cushion portion 20 of the seat 10.

The location for accommodating the adjustment mechanism may also dependon the degrees of freedom to be controlled. For example, in the case ofa degree of freedom related to the backrest portion 30, such ascontrolling lumbar support or adjustment of side bolsters of thebackrest portion 30, the adjustment mechanism could be arranged in thebackrest portion 30 of the seat 10. Similarly, in the case ofcontrolling a degree of freedom related to the seat cushion portion 20,such as adjustment of seat cushion length or adjustment of leg support,the adjustment mechanism could be arranged in the seat cushion portion20 of the seat 10. However, in some scenarios the adjustment mechanismcould also be located differently. For example, for controlling a degreerelated to the headrest 50, a part of the adjustment mechanism couldalso be arranged in the backrest portion 30. For controlling degrees offreedom relating to the headrest 50 and the backrest portion 30, theadjustment mechanism could also have components in accommodated in theheadrest 50 and components accommodated in the backrest portion 30.

In some implementations, the adjustment mechanism may use more thanthree screw shafts for controlling adjustment of the seat 10. In suchcases, each of the screw shaft may be used for controlling adjustment ofthe seat 10 according to at least one degree of freedom. As explainedabove, different ranges of linear motion of a nut element engaged withone of the screw shafts may be used for controlling multiple degrees offreedom with the same screw shaft. A clutch mechanism may be used forselectively controlling one or more of multiple screw shafts, and/orother types of drive shafts, by the same motor.

FIG. 8 illustrates a further example of a clutch mechanism 260 for anadjustment mechanism of the seat 10. The clutch mechanism to 160 may beused as an alternative or in addition to the above-mentioned clutchmechanism 160. As illustrated, the clutch mechanism 260 may be used forselectively driving multiple screw shafts 211, 212, 213, 214, 215 with asingle motor 250, e.g., an electronically controlled electric motor. Themotor 250 may for example be a brushless motor, e.g., using anelectronic commutation scheme. Implementing the motor 250 as a brushlessmotor may help to reduce noise and/or improve durability andreliability. Since the motor 250 is used for driving all screw shafts211, 212, 213, 214, 215 and usage of multiple motors is therefore notnecessary, excessive costs for using a brushless motor can be avoided.For at least one of the screw shafts 211, 212, 213, 214, 215, differentranges of linear motion of a nut element engaged with one of the screwshafts may be used for controlling multiple degrees of freedom, such asexplained in connection with FIGS. 2A, 2B, 2C, 3A, 3B, 3C, 4A, 4B, and5C.

In the clutch mechanism 260 the motor 250 uses a two-stage worm gear 255to drive a first gear wheel 261 and a first clutch wheel 262 on a driveshaft of the screw shaft 211. A second gear wheel 263 is arranged nextto the first clutch wheel 262 while being rotatable about the driveshaft of the screw shaft 211. Accordingly, a rotation of the second gearwheel 263 does not necessarily translate into a rotation of the driveshaft of the screw shaft 211. The first clutch wheel 262 and the secondgear wheel 263 have opposing axial faces which are configured to be usedfor selectively engaging the first clutch wheel 262 and the second gearwheel 263 by bringing the opposing axial faces together. As illustrated,this engagement may be achieved by interlocking of axial teeth of thefirst clutch wheel 262 and complementary axial teeth of the second gearwheel 263. For facilitating engagement and/or disengagement of the axialteeth with the complementary axial teeth, the axial teeth of the firstclutch wheel 262 and the complementary axial teeth of the second gearwheel 263 may have sloped mating faces, e.g., inclined by an angle of 5°or less with respect to the axial direction. Due to the sloped matingfaces, the axial teeth have an outer shape which tapers toward thesecond gear wheel 263 and fits into a narrowing gap between twoneighboring complementary teeth of the second gear wheel 263. However,other ways of engaging the opposing axial surfaces could be used aswell.

Next to the second gear wheel 263, a second clutch wheel 264 is arrangedon the drive shaft of the screw shaft 211. The second clutch wheel 264rotates together with the screw shaft 211. The second gear wheel 263 andthe second clutch wheel 264 have opposing axial faces which areconfigured to be used for selectively engaging the second gear wheel 263and the second clutch wheel 264 by bringing the opposing axial facestogether. As illustrated, this engagement may be achieved byinterlocking of axial teeth of the second clutch wheel 264 andcomplementary axial teeth of the second gear wheel 263. For facilitatingengagement and/or disengagement of the axial teeth with thecomplementary axial teeth, the axial teeth of the second clutch wheel264 and the complementary axial teeth of the second gear wheel 263 mayhave sloped mating faces, e.g., inclined by an angle of 5° or less withrespect to the axial direction. Due to the sloped mating faces, theaxial teeth have an outer shape which tapers toward the second gearwheel 263 and fits into a narrowing gap between two neighboringcomplementary teeth of the second gear wheel 263. However, other ways ofengaging the opposing axial surfaces could be used as well.

A third gear wheel 271 and a third clutch wheel 272 are arranged on adrive shaft of the screw shaft 212. The third gear wheel 271 is engagedwith and driven by the first gear wheel 261. The third clutch wheel 272rotates together with the third gear wheel 271 and is thus also drivenby the first gear wheel 261. A fourth gear wheel 273 is arranged next tothe third clutch wheel 272 while being rotatable about the drive shaftof the screw shaft 212. Accordingly, a rotation of the fourth gear wheel273 does not necessarily translate into a rotation of the drive shaft ofthe screw shaft 212. The third clutch wheel 272 and the fourth gearwheel 273 have opposing axial faces which are configured to be used forselectively engaging the third clutch wheel 272 and the fourth gearwheel 273 by bringing the opposing axial faces together. As illustrated,this engagement may be achieved by interlocking of axial teeth of thethird clutch wheel 272 and complementary axial teeth of the fourth gearwheel 273. For facilitating engagement and/or disengagement of the axialteeth with the complementary axial teeth, the axial teeth of the thirdclutch wheel 272 and the complementary axial teeth of the fourth gearwheel 273 may have sloped mating faces, e.g., inclined by an angle of 5°or less with respect to the axial direction. Due to the sloped matingfaces, the axial teeth have an outer shape which tapers toward thefourth gear wheel 273 and fits into a narrowing gap between twoneighboring complementary teeth of the fourth gear wheel 273. However,other ways of engaging the opposing axial surfaces could be used aswell.

Next to the fourth gear wheel 273, a fourth clutch wheel 274 is arrangedon the drive shaft of the screw shaft 212. The fourth clutch wheel 274rotates together with the screw shaft 212. The fourth gear wheel 273 andthe fourth clutch wheel 274 have opposing axial faces which areconfigured to be used for selectively engaging the fourth gear wheel 273and the fourth clutch wheel 274 by bringing the opposing axial facestogether. As illustrated, this engagement may be achieved byinterlocking of axial teeth of the fourth clutch wheel 274 andcomplementary axial teeth of the fourth gear wheel 273. For facilitatingengagement and/or disengagement of the axial teeth with thecomplementary axial teeth, the axial teeth of the fourth clutch wheel274 and the complementary axial teeth of the fourth gear wheel 273 mayhave sloped mating faces, e.g., inclined by an angle of 5° or less withrespect to the axial direction. Due to the sloped mating faces, theaxial teeth have an outer shape which tapers toward the fourth gearwheel 273 and fits into a narrowing gap between two neighboringcomplementary teeth of the fourth gear wheel 273. However, other ways ofengaging the opposing axial surfaces could be used as well.

A fifth gear wheel 275 is arranged on a drive shaft of the screw shaft213. The fifth gear wheel 275 is engaged with and driven by the fourthgear wheel 273. The fifth gear wheel 275 is rotatable about the driveshaft of the screw shaft 213. Accordingly, a rotation of the fifth gearwheel 275 does not necessarily translate into a rotation of the screwshaft 213. Next to the fifth gear wheel 275, a fifth clutch wheel 276 isarranged on the drive shaft of the screw shaft 213. The fifth clutchwheel 276 rotates together with the screw shaft 213. The fifth gearwheel 275 and the fifth clutch wheel 276 have opposing axial faces whichare configured to be used for selectively engaging the fifth gear wheel275 and the fifth clutch wheel 276 by bringing the opposing axial facestogether. As illustrated, this engagement may be achieved byinterlocking of axial teeth of the fifth clutch wheel 276 andcomplementary axial teeth of the fifth gear wheel 275. For facilitatingengagement and/or disengagement of the axial teeth with thecomplementary axial teeth, the axial teeth of the fifth clutch wheel 276and the complementary axial teeth of the fifth gear wheel 275 may havesloped mating faces, e.g., inclined by an angle of 5° or less withrespect to the axial direction. Due to the sloped mating faces, theaxial teeth have an outer shape which tapers toward the fifth gear wheel275 and fits into a narrowing gap between two neighboring complementaryteeth of the fifth gear wheel 275. However, other ways of engaging theopposing axial surfaces could be used as well.

A sixth gear wheel 281 is arranged on a drive shaft of the screw shaft214. The sixth gear wheel 281 is engaged with and driven by the secondgear wheel 263. The sixth gear wheel 281 is rotatable about the driveshaft of the screw shaft 214. Accordingly, a rotation of the sixth gearwheel 281 does not necessarily translate into a rotation of the screwshaft 214. A seventh gear wheel 282 is arranged next to the sixth gearwheel 281 while being rotatable about the drive shaft of the screw shaft214. Accordingly, a rotation of the seventh gear wheel 282 does notnecessarily translate into a rotation of the screw shaft 214. The sixthgear wheel 281 and the seventh gear wheel 282 have opposing axial faceswhich are configured to be used for selectively engaging the sixth gearwheel 281 and the seventh gear wheel 282 by bringing the opposing axialfaces together. As illustrated, this engagement may be achieved byinterlocking of axial teeth of the sixth gear wheel 281 andcomplementary axial teeth of the seventh gear wheel 282. Forfacilitating engagement and/or disengagement of the axial teeth with thecomplementary axial teeth, the axial teeth of the sixth gear wheel 281and the complementary axial teeth of the seventh gear wheel 282 may havesloped mating faces, e.g., inclined by an angle of 5° or less withrespect to the axial direction. Due to the sloped mating faces, theaxial teeth have an outer shape which tapers toward the seventh gearwheel 282 and fits into a narrowing gap between two neighboringcomplementary teeth of the seventh gear wheel 282. However, other waysof engaging the opposing axial surfaces could be used as well.

Next to the seventh gear wheel 282, a sixth clutch wheel 283 is arrangedon the drive shaft of the screw shaft 214. The sixth clutch wheel 283rotates together with the screw shaft 214. The seventh gear wheel 282and the sixth clutch wheel 283 have opposing axial faces which areconfigured to be used for selectively engaging the seventh gear wheel282 and the sixth clutch wheel 283 by bringing the opposing axial facestogether. As illustrated, this engagement may be achieved byinterlocking of axial teeth of the sixth clutch wheel 283 andcomplementary axial teeth of the seventh gear wheel 282. Forfacilitating engagement and/or disengagement of the axial teeth with thecomplementary axial teeth, the axial teeth of the sixth clutch wheel 283and the complementary axial teeth of the seventh gear wheel 282 may havesloped mating faces, e.g., inclined by an angle of 5° or less withrespect to the axial direction. Due to the sloped mating faces, theaxial teeth have an outer shape which tapers toward the seventh gearwheel 282 and fits into a narrowing gap between two neighboringcomplementary teeth of the seventh gear wheel 282. However, other waysof engaging the opposing axial surfaces could be used as well.

An eighth gear wheel 284 is arranged on a drive shaft of the screw shaft215. The eighth gear wheel 284 is engaged with and driven by the seventhgear wheel 282. The eighth gear wheel 284 is rotatable about the driveshaft of the screw shaft 215. Accordingly, a rotation of the eighth gearwheel 284 does not necessarily translate into a rotation of the screwshaft 215. Next to the eighth gear wheel 284, a seventh clutch wheel 285is arranged on the drive shaft of the screw shaft 215. The seventhclutch wheel 285 rotates together with the screw shaft 215. The eighthgear wheel 284 and the seventh clutch wheel 285 have opposing axialfaces which are configured to be used for selectively engaging theeighth gear wheel 284 and the seventh clutch wheel 285 by bringing theopposing axial faces together. As illustrated, this engagement may beachieved by interlocking of axial teeth of the seventh clutch wheel 285and complementary axial teeth of the eighth gear wheel 284. Forfacilitating engagement and/or disengagement of the axial teeth with thecomplementary axial teeth, the axial teeth of the seventh clutch wheel285 and the complementary axial teeth of the eighth gear wheel 284 mayhave sloped mating faces, e.g., inclined by an angle of 5° or less withrespect to the axial direction. Due to the sloped mating faces, theaxial teeth have an outer shape which tapers toward the eighth gearwheel 284 and fits into a narrowing gap between two neighboringcomplementary teeth of the eighth gear wheel 284. However, other ways ofengaging the opposing axial surfaces could be used as well.

The clutch mechanism 260 can be brought into various different states,depending on whether the above-mentioned clutch wheels or gear wheelsare engaged with each other. The screw shaft 211 is driven by the motor250 if the first clutch wheel 262 is engaged with the second gear wheel263 and the second clutch wheel 264 is engaged with the second gearwheel 263. The screw shaft 212 is driven by the motor 250 if the thirdclutch wheel 272 is engaged with the fourth gear wheel 273 and thefourth clutch wheel 274 is engaged with the fourth gear wheel 273. Thescrew shaft 213 is driven by the motor 250 if the fifth clutch wheel 276is engaged with the fifth gear wheel 275 and the fourth gear wheel 273is engaged with the third clutch wheel 272. The screw shaft 214 isdriven by the motor 250 if the sixth clutch wheel 283 is engaged withthe seventh gear wheel 282, the seventh gear wheel 282 is engaged withthe sixth gear wheel 281, and the second gear wheel 263 is engaged withthe first clutch wheel 262. The screw shaft 215 is driven by the motor250 if the seventh clutch wheel 285 is engaged with the eighth gearwheel 284, the seventh gear wheel 282 is engaged with the sixth gearwheel 281, and the second gear wheel 263 is engaged with the firstclutch wheel 262.

Further, each of the screw shafts 211, 212, 213, 214, 215 can bedisengaged from the motor 250: By disengaging the second clutch wheel264 from the second gear wheel 263, the screw shaft 211 can bedisengaged from the motor 250, while at the same time allowing any otherof the screw shafts 212, 213, 214, 215 to be engaged with the motor 250.By disengaging the fourth clutch wheel 274 from the fourth gear wheel273, the screw shaft 212 can be disengaged from the motor 250, while atthe same time allowing any other of the screw shafts 211, 213, 214, 215to be engaged with the motor 250. By disengaging the fifth clutch wheel276 from the fifth gear wheel 275, the screw shaft 213 can be disengagedfrom the motor 250, while at the same time allowing any other of thescrew shafts 211, 212, 214, 215 to be engaged with the motor 250. Bydisengaging the sixth clutch wheel 283 from the seventh gear wheel 282,the screw shaft 214 can be disengaged from the motor 250, while at thesame time allowing any other of the screw shafts 211, 212, 213, 215 tobe engaged with the motor 250. By disengaging the seventh clutch wheel285 from the eighth gear wheel 284, the screw shaft 215 can bedisengaged from the motor 250, while at the same time allowing any otherof the screw shafts 211, 212, 213, 214 to be engaged with the motor 250.

Accordingly, by providing each of the screw shafts 211, 212, 213, 214,215 with at least one gear wheel which is rotatable about a drive shaftof the respective screw shaft 211, 212, 213, 214, 215 and with a clutchwheel which rotates together with the screw shaft and can be selectivelyengaged with the respective gear wheel, the clutch mechanism 260 canflexibly support various states. As further can be seen from the clutchmechanism 260, gear wheels on one drive shaft may be used for drivingother drive shafts and at the same time be used for selective engagementwith a clutch wheel or other gear wheel. This allows for a compact andefficient implementation of the clutch mechanism 260.

In the clutch mechanism 260, multiple actuators may be used forselectively engaging the clutch wheels and gear wheels as describedabove. These actuators may be implemented as solenoid actuators, similaras described for the above-mentioned actuator 170. However, other typesof actuators could be used as well, such as SMA based actuators. Theclutch mechanism 260 could also use a combination of two or moredifferent types of actuators, such as a combination of solenoid basedactuators and SMA based actuators. Further, it is also possible to useone actuator for engaging more than one pair of wheels, such asdescribed for the above-mentioned actuator 170.

FIG. 9 illustrates a still further clutch mechanism 360 which may beused in an adjustment mechanism as explained above, e.g., in addition oras an alternative to the above-mentioned clutch mechanism 160 or 260. Asillustrated, the clutch mechanism 260 may be used for selectivelydriving multiple screw shafts 311, 312 with a single motor 350, e.g., anelectronically controlled electric motor. The motor 350 may for examplebe a brushless motor, e.g., using an electronic commutation scheme.Implementing the motor 350 as a brushless motor may help to reduce noiseand/or improve durability and reliability. Since the motor 350 is usedfor driving both screw shafts 311, 312 and usage of multiple motors istherefore not necessary, excessive costs for using a brushless motor canbe avoided. For at least one of the screw shafts 311, 312, differentranges of linear motion of a nut element engaged with one of the screwshafts may be used for controlling multiple degrees of freedom, such asexplained in connection with FIGS. 2A, 2B, 2C, 3A, 3B, 3C, 4A, 4B, and5C.

In the clutch mechanism 360, the motor 350 uses a two-stage worm gear355 to drive the screw shaft 311. A first gear wheel 361 rotatingtogether with the screw shaft 311 is used to drive a second gear wheel362. The second gear wheel 362 is arranged on a drive shaft of the screwshaft 312, while being rotatable about the drive shaft of the screwshaft 312. Accordingly, a rotation of the second gear wheel 362 does notnecessarily translate into a rotation of the screw shaft 312. Next tothe second gear wheel 362, a clutch wheel 363 is arranged on thedriveshaft of the screw shaft 312. The clutch wheel 363 rotates togetherwith the screw shaft 312. The second gear wheel 362 and the clutch wheel363 have opposing axial faces which are configured to be used forselectively engaging the clutch wheel 363 with the second gear wheel 362by bringing the opposing axial faces together. As illustrated, thisengagement may be achieved by interlocking of axial teeth of clutchwheel 363 and complementary axial teeth of the second gear wheel 362.For facilitating engagement and/or disengagement of the axial teeth withthe complementary axial teeth, the axial teeth of the clutch wheel 363and the complementary axial teeth of the second gear wheel 362 may havesloped mating faces, e.g., inclined by an angle of 5° or less withrespect to the axial direction. Due to the sloped mating faces, theaxial teeth have an outer shape which tapers toward the second gearwheel 362 and fits into a narrowing gap between two neighboringcomplementary teeth of the second gear wheel 362. However, other ways ofengaging the opposing axial surfaces could be used as well.

In the clutch mechanism 360, the engagement of the clutch wheel 363 withthe second gear wheel 362 is controlled by an SMA based actuator 370. Asillustrated, the SMA based actuators 370 includes an SMA wire 371 and anelectronically controlled heater 372. In response to heating of the SMAwire 371 by the heater 372, the SMA wire 371 changes its length. Forexample, the SMA wire 371 may shorten in response to heating by theheater 372. Shortening of the SMA wire 371 actuates a lever 373 whichpushes the second gear wheel 362 in an axial direction towards theclutch wheel 363, thereby engaging the clutch wheel 363 with the secondgear wheel 362. In response to cooling of the SMA wire 371, the lengthof the SMA wire 371 increases, thereby moving the second gear wheel 362away from the clutch we have 363 and thus disengaging the clutch wheelthree and 63 from the second gear wheel 362. In the illustrated example,the lever 373 is formed of two parts which are flexibly connected toeach other. This allows for avoiding excessive stress, e.g., if thelever 373 pushes the second gear wheel 362 towards the clutch wheel 363while the axial teeth of the second gear wheel 362 and the complementaryaxial teeth of the clutch wheel 363 are misaligned and thus impairmovement of the second gear wheel 362 towards the clutch wheel 363.

In the clutch mechanism 360, both screw shafts 311, 312 are driven bythe motor 350 if the clutch wheel 363 is engaged with the second gearwheel 362. If the clutch wheel 363 is disengaged from the second gearwheel 362, only the screw shaft 311 is driven by the motor 350. This mayfor example be useful for both controlling vertical position of thelumbar support 40 of the seat 10 and arching of the lumbar support 40 ofthe seat: Driving both screw shafts 311 and 312 may be used foradjustment of the vertical position of the lumbar support 40, whiledriving only one of the screw shafts 311 and 312 may be used foradjustment of the arching. For this purpose, nut elements on the screwshafts 311 and 312 may be coupled to different engagement points on thelumbar support 40, so that relative movement of these engagement pointswith respect to each other causes parking of the lumbar support 40.Different ranges of movement of at least one of the nut elements may beused for controlling one or more additional degrees of freedom foradjustment of the seat 10,

While exemplary embodiments have been described in the context of avehicle seat, the adjustment mechanisms and seats according toembodiments of the invention are not limited to this particularapplication. Rather, adjustment mechanisms as explained above may beemployed in a wide variety of seats. Further, it is noted that theillustrated adjustment mechanisms may be modified in various ways. Byway of example, the adjustment mechanisms could include various numbersof screw shafts and be accommodated within various parts of the seat.Further, one or more of the screw shafts could be replaced by otherkinds of shafts, e.g., torsion shafts, or other additional types ofshafts could be used to supplement the above-mentioned screw shafts andbe driven by the same motor. Further, one or more of the screw shaftscould or other shafts could also be flexible or include flexibleportions. Accordingly, the above-described clutch mechanisms may be usedfor driving screw shafts, but also for driving various other types ofdrive shafts, in addition or as an alternative to screw shafts asdescribed above. In some cases such screw shafts or drive shafts mayalso extend from one part of the seat to another part of the seat, e.g.,from the backrest portion to the headrest or vice versa. Further, it isalso possible to use an adjustment mechanism which is distributed overmultiple parts of the seat 10, e.g., by accommodating some components ofthe adjustment mechanism in the backrest portion 30 of the seat 10 andaccommodating other components of the adjustment mechanism in theheadrest 50 and/or the seat cushion portion 20 of the seat 10. Further,adjustment mechanisms as explained above may be used for adjustment of aseat with respect to various combinations of degrees of freedom. Forexample, using similar principles as explained above for the tilting ofthe side bolsters, tilting of the headrest, e.g., as denoted by HT inFIG. 1A, could be implemented by using different ranges of linearmovement of a nut element on the same screw shaft. Forward tilting ofthe headrest 50 could then for example start when the headrest 50 hasreached its maximum upward position.

The invention claimed is:
 1. An adjustment mechanism for a seat, theadjustment mechanism comprising: at least one screw shaft; a motor fordriving the at least one screw shaft; and at least one nut elementengaged with the at least one screw shaft, wherein rotation of the atleast one screw shaft caused by the motor translates into linear motionof the at least one nut element, and wherein in a first range of linearmotion of the at least one nut element the linear motion translates intoadjustment of the seat according to a first degree of freedom and in asecond range of linear motion of the at least one nut element the linearmotion translates into adjustment of the seat according to a seconddegree of freedom.
 2. The adjustment mechanism according to claim 1,wherein the first degree of freedom corresponds to displacement of aheadrest of the seat in a horizontal direction or to tilting of theheadrest.
 3. The adjustment mechanism according to claim 2, wherein theheadrest comprises at least one flap element pivotable with respect to amain portion of the headrest and the second degree of freedomcorresponds to pivoting of the at least one flap element with respect tothe main portion of the headrest.
 4. The adjustment mechanism accordingto claim 3, wherein the headrest comprises a first flap elementpivotable with respect to the main portion of the headrest and a secondflap element pivotable with respect to the main portion of the headrest,and the second degree of freedom corresponds to pivoting of the firstflap element and the second flap element with respect to the mainportion of the headrest.
 5. The adjustment mechanism according to claim4, further including a first nut element engaged with the at least onescrew shaft; and a second nut element engaged with the at least onescrew shaft, wherein rotation of the at least one screw shaft caused bythe motor translates into linear motion of the first nut element andlinear motion of the second nut element, wherein in a first range of thelinear motion of the first nut element and a first range of the linearmotion of the second nut element the linear motion of the first nutelement and of the second nut element translates into adjustment of theseat according to the first degree of freedom, and wherein in a secondrange of the linear motion of the first nut element the linear motion ofthe first nut element translates into pivoting of the first flap elementwith respect to the main portion of the headrest, and wherein in asecond range of the linear motion of the second nut element the linearmotion of the second nut element translates into pivoting of the secondflap element with respect to the main portion of the headrest.
 6. Theadjustment mechanism according to claim 3, wherein the tilting of the atleast one flap element is about a vertical tilt axis.
 7. The adjustmentmechanism according to claim 1, wherein the at least one screw shaft isarranged in a horizontal direction.
 8. The adjustment mechanismaccording to claim 1, further including at least one further screwshaft; and a clutch mechanism for selectively engaging the motor withone or more of the at least one screw shaft and the at least one furtherscrew shaft; wherein rotation of the at least one further screw shaftcaused by the motor translates into adjustment of the seat according toa third degree of freedom.
 9. The adjustment mechanism according toclaim 8, wherein the clutch mechanism comprises at least one solenoidactuator for switching the clutch mechanism between a first state inwhich the motor is engaged with one or more of the screw shafts and asecond state in which the motor is not engaged with the one or more ofthe screw shafts.
 10. The adjustment mechanism according to claim 8,wherein the clutch mechanism comprises at least one shape memory alloyactuator for switching the clutch mechanism between a first state inwhich the motor is engaged with one or more of the screw shafts and asecond state in which the motor is not engaged with the one or more ofthe screw shafts.
 11. The adjustment mechanism according to claim 8,wherein the third degree of freedom corresponds to displacement of aheadrest of the seat in a vertical direction.
 12. The adjustmentmechanism according to claim 8, wherein the at least one screw shaft isarranged in a horizontal direction and the at least one further screwshaft is arranged in a vertical direction.
 13. The adjustment mechanismaccording to claim 8, wherein the adjustment mechanism is configured tobe accommodated within a headrest of the seat.
 14. A seat comprising atleast one adjustment mechanism, wherein the at least one adjustmentmechanism includes at least one screw shaft; a motor for driving the atleast one screw shaft; and at least one nut element engaged with the atleast one screw shaft, wherein rotation of the at least one screw shaftcaused by the motor translates into linear motion of the at least onenut element, and wherein in a first range of linear motion of the atleast one nut element the linear motion translates into adjustment ofthe seat according to a first degree of freedom and in a second range oflinear motion of the at least one nut element the linear motiontranslates into adjustment of the seat according to a second degree offreedom.
 15. The seat according to claim 14, wherein the seat comprisesa headrest and the adjustment mechanism is accommodated within theheadrest.